In order to save execution time, prefer smaller input files.
Some input files are a few hundred lines, but others are way bigger.
Each time a Phantom launches, it needs to load the input spreadsheet.
Be aware that it takes about 1 second to load 1000 lines. So if your file is under 10k or 20k lines, that's alright.
But some of our users are loading 2M+ lines files at each Launch. This means 30+ minutes of loading time per Launch.
Prefer dividing big files in 30k sheets in order to save on your execution time!